1. Field of the Invention
This invention relates, in general, to voltage regulators and, more specifically, to D.C. voltage regulators.
2. Description of the Prior Art
Electronic apparatus, such as computers, digital logic systems and similar applications, require highly reliable power supplies having precisely regulated output voltages. In order to regulate, or maintain the output voltage at a constant magnitude, voltage regulators are commonly utilized which could include a switching device, such as a transistor, for periodically transferring energy from a power source to a storage means, such as an inductor. When the transistor is turned off, i.e., made non-conductive, the current which has built up in the inductor is transferred to the load or utilization device.
In a prior art regulator, known as a switching regulator, the transistor is opened cyclically and at a constant frequency, with the time intervals between openings being apportioned in response to the magnitude of the output voltage of the regulator. More specifically, if the output voltage drops below a desired level, the switching device is connected to the inductor for a greater proportion of a given cycle so that the inductor current builds up to a higher value than when the build-up time is less. The higher current stored in the inductor causes the output voltage of the regulator to be raised to the desired level.
However, such prior art regulators have distinct disadvantages. The first of these is the low efficiency of the regulators due to the need for circuits to remove the stored base charge from the output transistors which, in so doing, require power from the regulator circuit. Secondly, the number and size of the components required to construct a reliable switching regulator has restricted the use of such devices to bulk power supplies for electronic apparatus. In such applications, it is a common practice to have a bulk D.C. power supply at a location remote from the power utilization devices which, in electronic art, are typically printed circuit boards mounted in a rack. The bulk power is then carried by a conducting cable and a series fuse from the bulk supply to the individual circuit boards. Since there exists a voltage drop across both the fuse and the cable, the power supplied to the printed circuit boards is a small percentage below the desired magnitude, which lowers the efficiency and reliable operation of the electronic components connected thereto.
Thus, it would be desirable to provide a voltage regulator for providing a precisely regulated D.C. voltage at its output that is more efficient than prior art regulators. It would be also desirable to provide a voltage regulator that provides better regulation of the magnitude of the output voltage than prior art regulators. It is also desirable to provide a voltage regulator that is constructed of fewer parts than similar devices. Finally, it would be desirable to provide a voltage regulator that can be placed on a printed circuit board and disposed in a rack adjacent to the power utilization electronic printed circuit boards.